Pressure measuring method and device

ABSTRACT

The invention provides a pressure measuring method and device that are capable of easily measuring the volume of a pipe that is an object of inspection and of eliminating the influences of a change in temperature in the pipe.  
     A pressure measuring method using a pressure sensor  4  connected to a pipe for feeding a gas thorough a connecting portion for measuring the pressure in the pipe, the method being characterized in that the method comprises a pressurizing step for pressurizing the inside of the pipe by a pump  5  with the pipe held in the closed state, and a step for measuring an amount of pressure change of the pipe in the standing state after completion of the pressurization step, and in that an amount of pressurization change of the in-pipe pressure by the pressurization step, and the flow rate of the gas fed into the pipe during pressurization are measured, and the volume of the pipe in the closed state is calculated on the basis of the amount of pressurization change and the flow rate of the gas, and the amount of leakage of the gas from the pipe is calculated on the basis of the volume of the pipe and the amount of pressure change in the standing state.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a pressure measuring method and devicethat measure the pressure in a pipe, which are used for diagnosing thecondition of the pipe feeding gas or liquid. In particular, it relatesto the pressure measuring method and device that detect leakage of a gasor a liquid from the pipe.

2. Related art statement

Many pipes are installed in buildings of home and factory, and these areutilized for supplying various gases or various liquids, such as towngas, liquefied petroleum gas, potable water, refrigerant for airconditioning, gas and solution for plant, to every place in a building.

However, by mechanical or chemical action, these pipes may bedeteriorated gradually when being used over a long period of time, andpossibly there may occur a problem that an opening is generated in awall of the pipe and a gas or a liquid carried inside the pipe isleaked.

Therefore, periodical leakage inspections of many of these pipes aremade compulsory by decree, etc. For example, when consumer usesliquefied petroleum gas (LP gas), an inspection of facilities, such as apipe, is made compulsory by “Law Concerning the Securing of Safety andthe Adequacy of Transaction for Liquefied Petroleum Gas (common name:Liquefied Petroleum Gas Law)”.

So far, the leakage inspection of a pipe has been conducted by holdingthe pipe in the closed state, injecting a gas or a liquid from an inlet,such as a feed opening or an exhaust, that is installed in a part of thepipe and is communicated with the inside of the pipe, making the insideof the pipe higher pressure condition than the outside of the pipe, andthen, measuring the pressure change in the pipe beyond the predeterminedtime.

Then, in the result of the measurement, for example, if it is shown thatpressure is on a downward trend, it is assumed that the gas or theliquid is flowing out of the inside of the pipe, and it is judgedaccordingly that there is an opening, such as crack in a part of thewall of the pipe.

In addition, it takes a different amount of time for an inspectiondepending on the volume of the pipe that is being inspected. There is atendency, generally, that the bigger the volume of the pipe is, thelonger it takes for inspection.

Moreover, in order to measure the amount of leakage of a gas or aliquid, since it is not possible to calculate only by measuring thepressure change in a pipe, it is necessary to calculate the volume ofthe pipe in the closed state separately.

However, on the grounds that the volume of the pipe that is an object ofinspection cannot be easily measured for real, in case of inspecting adomestic gas piping etc., inspection providers set the measuring timeamount by estimating the volume of the pipe experientially orintuitively, and utilize the volume of a pipe calculated based on anengineering-drawing of a pipe work etc. for the measurement of leakageamount. Therefore it makes it difficult to improve the accuracy of theinspection sufficiently.

Furthermore, the pressure change in the pipe held in the closed state isnot caused only by leakage, but the pressure changes due to a change intemperature etc. in the pipe.

Therefore, the measurement in consideration of the influences of thistemperature change is required for an accurate inspection, however, asthere exists no easy-to-use measurement device up to now that canmeasure the temperature change in a pipe simultaneously with themeasurement of the pressure change of the pipe, the measurement has beenconducted by selecting the time when a temperature change is small, andit has been the cause of the operation efficiency of the inspectionfalling remarkably.

The present invention intends to solve the above-mentioned objects andto provide the pressure measuring method and device that are capable ofeasily measuring the volume of a pipe that is an object of inspectionand of eliminating the influences of a change in temperature in thepipe.

Further, as to the pressure measuring device of the present invention,it intends to provide the functions and the structure for preventing theoperation of the pressure measuring device from cumbersomeness and thesaid device from complication, even when adding new functions, such asthe measurement of the pipe volume or the elimination of the influencesof a change in temperature.

Also, by displaying the past measurement results of each client andenabling the comparison of the present measurement value with the pastmeasurement results, it intends to provide a diverse and novelinspection method of a pipe, with which the longitudinal change can beobserved, or on which is based in evaluating the abnormality of thepresent measurement value, etc.

SUMMARY OF THE INVENTION

In order to solve the above-mentioned problems, the invention related toclaim 1 has following features. A pressure measuring method which, bythe connection to a pipe for feeding a gas or a liquid, measures thepressure in the said pipe, comprises a pressurizing and depressurizingstep for pressurizing or depressurizing the inside of the pipe held inthe closed state, and a step for measuring an amount of pressure changeof the pipe in the standing state after completion of the saidpressurizing and depressurizing step, wherein an amount ofpressurization and depressurization change of the in-pipe pressure bythe said pressurizing and depressurizing step or an additionalpressurizing and depressurizing step, and the flow rate of the gas orthe liquid which is fed into, or discharged from the pipe during thepressurization or the depressurization, are measured, the volume of thepipe in the closed state is calculated on the basis of the said amountof pressurization and depressurization change, and the said flow rate ofthe gas or the liquid, and the amount of leakage of the gas or theliquid from the pipe is calculated on the basis of the said volume ofthe pipe and the said amount of pressure change in the standing state.

The invention related to claim 2 has following features. A pressuremeasuring method which, by the connection to a pipe for feeding a gas ora liquid, measures the pressure in the said pipe, comprises apressurizing and depressurizing step for pressurizing or depressurizingthe inside of the pipe held in the closed state, and a step formeasuring an amount of pressure change of the pipe in the standing stateafter completion of the said pressurizing and depressurizing step,wherein before the said pressurizing and depressurizing step or aftercompletion of the measurement of the amount of pressure change in thestanding state, the said pipe is closed after adjusting the in-pipepressure to the pressure outside the pipe, and the amount of pressurechange in the pipe due to a temperature change is measured, and thevalue of the said amount of pressure change in the standing state isamended in accordance with the said amount of pressure change due to thetemperature change, and the influences of the temperature change on thepressure change in the standing state are eliminated.

The invention related to claim 3 has following features. A pressuremeasuring method which, by the connection to a pipe for feeding a gas ora liquid, measures the pressure in the said pipe, comprises apressurizing and depressurizing step for pressurizing or depressurizingthe inside of the pipe held in the closed state, and a step formeasuring an amount of pressure change of the pipe in the standing stateafter completion of the said pressurizing and depressurizing step,wherein before the said pressurizing and depressurizing step or aftercompletion of the measurement of the amount of pressure change in thestanding state, the said pipe is closed after adjusting the in-pipepressure to the pressure outside the pipe, and the amount of pressurechange in the pipe due to a temperature change is measured, an amount ofpressurization and depressurization change of the in-pipe pressure bythe said pressurizing and depressurizing step or an additionalpressurizing and depressurizing step, and the flow rate of the gas orthe liquid which is fed into, or discharged from the pipe during thepressurization or the depressurization, are measured, the volume of thepipe in the closed state is calculated on the basis of the said amountof pressurization and depressurization change, and the said flow rate ofthe gas or the liquid, the value of the said amount of pressure changein the standing state is amended in accordance with the said amount ofpressure change due to the temperature change, and the amount of leakageof the gas or the liquid from the pipe is calculated on the basis of thesaid amended amount of the pressure change in the standing state and thesaid volume of the pipe.

The invention related to claim 4 has following features. A pressuremeasuring method which, by the connection to a pipe for feeding a gas ora liquid, measures the pressure in the said pipe, comprises apressurizing and depressurizing step for pressurizing or depressurizingthe inside of the pipe held in the closed state, and a step formeasuring an amount of pressure change of the pipe in the standing stateafter completion of the said pressurizing and depressurizing step,wherein before the said pressurizing and depressurizing step, the saidpipe is closed after adjusting the in-pipe pressure to the pressureoutside the pipe, and the amount of pressure change in the pipe due to atemperature change is measured, the predicted value of the said amountof pressure change in the standing state is calculated in accordancewith the said amount of pressure change due to the temperature change,and leakage condition of the said pipe is judged by comparing the saidpredicted value with the actually-measured amount of pressure change inthe standing state.

The invention related to claim 5 has following features. A pressuremeasuring method which, by the connection to a pipe for feeding a gas ora liquid, measures the pressure in the said pipe, comprises apressurizing and depressurizing step for pressurizing or depressurizingthe inside of the pipe held in the closed state, and a step formeasuring an amount of pressure change of the pipe in the standing stateafter completion of the said pressurizing and depressurizing step,wherein the value of the said amount of pressure change is amended onthe basis of the amount of change of the actually-measured temperatureof the gas or the liquid in the pipe or the actually-measuredtemperature of the pipe, and the influences of the temperature change onthe pressure change in the standing state are eliminated.

The invention related to claim 6 has following features. A pressuremeasuring method which, by the connection to a pipe for feeding a gas ora liquid, measures the pressure in the said pipe, comprises apressurizing and depressurizing step for pressurizing or depressurizingthe inside of the pipe held in the closed state, and a step formeasuring an amount of pressure change of the pipe in the standing stateafter completion of the said pressurizing and depressurizing step,wherein an amount of pressurization and depressurization change of thein-pipe pressure by the said pressurizing and depressurizing step or anadditional pressurizing and depressurizing step, and the flow rate ofthe gas or the liquid which is fed into, or discharged from the pipeduring the pressurization or the depressurization, are measured, thevolume of the pipe in the closed state is calculated on the basis of thesaid amount of pressurization and depressurization change, and the saidflow rate of the gas or the liquid, the value of the said amount ofpressure change in standing state is amended on the basis of the amountof change of the actually-measured temperature of the gas or the liquidin the pipe or the actually-measured temperature of the pipe, and theamount of leakage of the gas or the liquid from the pipe is calculatedon the basis of the said amended amount of pressure change in standingstate and the said volume of the pipe.

The invention related to claim 7 has following feature. The pressuremeasuring method as claimed in claims 1, 3, and 6, is characterized inthat at least one of the actually-measured temperature of the gas or theliquid that is fed into a pipe, and the actually-measured temperature ofthe gas or the liquid that is discharged from the said pipe, is used incalculating the said volume of the pipe.

The invention related to claim 8 has following feature. The pressuremeasuring method as claimed in claims 2, 3, and 4, is characterized inthat in measuring the said amount of pressure change in the standingstate, the said amount of pressure change is re-amended on the basis ofthe amount of change of the actually-measured temperature of the gas orthe liquid in the pipe, or the actually-measured temperature of thepipe.

The invention related to claim 9 has following feature. The pressuremeasuring method as claimed in claims 1 to 6, is characterized in thatwhen measuring the pressure several times, the said pressurizing anddepressurizing step is conducted by doing the pressure measurement inpressurization condition and the pressure measurement indepressurization condition in combination.

The invention related to claim 10 has following feature. The pressuremeasuring method as claimed in claims 1, 3, and 6, is characterized inthat the amount of time for measuring the said amount of pressure changeof the pipe in the standing state is decided in accordance with thevalue of the said volume of the pipe.

The invention related to claim 11 has following feature. The pressuremeasuring method as claimed in claims 1 to 6, is characterized in thatthe said amount of pressure change is calculated by approximatingseveral measurement values by straight line.

The invention related to claim 12 has following feature. The pressuremeasuring device uses the pressure measuring method as claimed in claims1 to 11.

The invention related to claim 13 has following feature. The pressuremeasuring device as claimed in claim 12, includes a pressurizing meansfor pressurizing the inside of the pipe in the inside of said pressuremeasuring device.

The invention related to claim 14 has following feature. The pressuremeasuring device as claimed in claims 12 and 13, includes a display partplaced in the said pressure measuring device, which displays at leastone of the numerical values measured or calculated by the said pressuremeasuring device, information of operator guidance or operatingcondition of the said pressure measuring device, and the past result ofthe measurement or calculation.

The invention related to claim 15 has following feature. The pressuremeasuring device as claimed in claims 12 to 14, includes a memorizingmeans which accumulates the numerical values measured or calculated.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram of the pressure measuring device of thepresent invention.

FIG. 2 is an external view of the pressure measuring device of thepresent invention.

FIG. 3 is a block diagram of the electronic circuitry of the pressuremeasuring device of the present invention.

FIG. 4 is a flowchart drawing concerning the operation of the pressuremeasuring device of the present invention.

FIG. 5 is an example of the measurement result by the pressure measuringdevice of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The preferable embodiments of the present invention will be explainedhereinafter centering on the pressure measuring device for the leakageinspection of gas piping.

Fig. is a schematic diagram showing the concept of the mechanicalcompositions of the pressure measuring device of the present invention.

In the pressure measuring device, the electric pump 5 for supplying airinto a pipe, the pressure sensor 4 for measuring the pressure in thepipe, the valve or check valve 3 for controlling the air amount suppliedinto the pipe, and the valve 7 for equalizing the pressure in the pipeto an atmospheric pressure, are mutually connected and arranged in thecoupling structure of the pipe as in FIG. 1.

The inspection hose 2 runs out from the pressure measuring device. In aninspection, as shown in connecting portion 1, the front end of theinspection hose 2 is connected to an exhaust of the gas cock installedin the gas piping that is an object of inspection.

Although not shown in FIG. 1, by placing a temperature sensor detectingthe temperature of a gas in the pipe area closed by the connectingportion 1, the valve or checking valve 3, the valve 7, and the pressuresensor 4, it is possible to measure the temperature of the gas that isfed into pipe area, or discharged from the pipe area, and at the sametime, to measure the gas temperature in the pipe when measuring theamount of pressure change.

Also, it is possible to measure the temperature of a pipe directlyinstead of the temperature measurement of a gas. In this case, thedevice can be configured to measure the temperature of the pipe bysetting a temperature sensor in the contact zone of the pipe and theconnecting portion 1, or installing a temperature sensor separately fromthe body of the pressure measuring device and connecting the saidtemperature sensor to the pipe that is an object of inspection.

In addition, when conducting an inspection of the pipe with the samevolume as the gas piping of general homes, it is more convenient, incarrying and handling it, to incorporate the electric pump 5 into thepressure measuring device. However, if the volume of pipe is large, suchas the plant pipe of a factory, it is preferable to install a pressuremeasuring device and an electric pump separately and to enable themutual connection of the pipes of each equipment, as the amount of airetc. supplied to the pipe are increased.

The controller 6 performs control of drive of the electric pump 5,control of gating of the valve 3 and 7, and inspections of the pressuresignal of the pressure sensor 4. By means of control of the controller6, the measurement of a pipe volume, the measurement of leakage amountof a pipe, and various inspections of adjustment pressure, combustionpressure, blockade pressure, etc. are practiced as explainedhereinafter.

FIG. 2 shows the exterior of a pressure measuring device. However, thepressure measuring device of the present invention is not limited to theexterior shown in FIG. 2. The exterior of it can be changed by modifyingaccording to need, the arrangement and the figuration of various membershereinafter described.

The whole pressure measuring device is in the size that can be held byone hand so that it may be easy for inspection providers to handle.

The KEY board 9 incorporates the liquid crystal display part 8displaying measurement values, calculation values, graphs of measurementresults, and the operating procedure etc., the power source (POWER) key,the starting (START) key, the SET key, the entering (ENT) key, thedeleting (DEL) key, numeric keypad, and the navigation key for movingcursors and displays, on the upper side. Selection of an inspectionmode, input of customer codes or numeric values, etc. are conductedusing the various keys of the said KEY board. In addition, in order toenable the input of various information, the input function of thealphabet and the kana character by utilizing numeric keypad can be addedif needed, which is used in cellular phones etc.

It is also possible to make the liquid crystal display part 8self-luminous type display unit, such as display part with backlight ororganic electroluminescence display, in preparation for inspectingoperation in a dark place.

Also, although not shown in FIG. 2, the measurement results etc. can beprinted out by incorporating an printer, such as thermal printer,integrally into the pressure measuring device if required.

From the topside of the pressure measuring device, the connectingportion 1 connected to the pipe that is an object of inspectionprotrudes through the inspection hose 2. The shape and the material ofthe protruding inspection hose 2 is selected by considering the lengthand ductility of it for easy connection to the pipe inspected, anddurability against handling environment. Also, it is possible to attachthe connecting means, which is used in most commercially produced stoveburners or gas burners, to connecting portion 1, in order that theconnecting portion 1 can be attached to the front end of a gas piping atthe flip of a switch.

In addition, in case of measuring the adjustment pressure, combustionpressure, and blockade pressure that are legal items of inspection of LPgas, the inspection can be implemented by connecting the front end ofconnecting portion 1 to a part of pipes that diverge from the pipeconnecting between a burning appliance, such as a stove burner, and agas cock.

15 is an exhaust hole, which is for discharging the gas in a pressuremeasuring device into air through the valve 7 in FIG. 1. The exhausthole 15 may be installed wherever on the external case of the pressuremeasuring device. By opening the valve 7, it is used in case the offset(the atmospheric pressure is set as 0 value) of the pressure sensor 4 isconducted, besides the function for equalizing the pressure in theinspected pipe with the outside pressure (the atmospheric pressure).

FIG. 3 is a block diagram of the electronic circuit in the pressuremeasuring device.

Driving of the controller 6 is performed along the programs of variousinspection modes that are incorporated into CPU 6′.

CPU 6′ is supplied with electric power through the power supply unit 13and the electric power is supplied to pump 5 or valve 3, 7 at the righttime by the direction of CPU 6′. In addition, electric power can beintroduced from general household power source as power supply insteadof electric battery.

The detection signal from the pressure sensor 4 is digitalized throughA/D converter and inputted to CPU 6′.

Also, although not shown in FIG. 3, the detection signal from atemperature sensor for measuring the temperature of the gas in a pipe,which is fed into, or discharged from the pipe, or the temperature ofthe pipe itself, is digitalized through A/D converter and inputted toCPU 6′.

Furthermore, the memorizing means 10 may be configured to accumulate themeasurement results of each customer, and then, by retrieving them byCPU 6′ if required, to display them on the liquid crystal display part8, or by communication method such as a cable that is not shown in thefigure, to send the data to outside PCs, mobile phones, etc. Meanwhile,it is also possible to accumulate data in the said memorizing means 10by downloading them from PC etc.

Next, the algorithm of the leakage inspection used in the pressuremeasuring method of the present invention will be explained.

If the pressure in a pipe is set as P and the atmospheric pressure of aninspection area is set as P₀, the differential pressure (P−P₀) in thepipe will generally change as time advances. By measuring the change,the gas leakage from the inside of the pipe is detected.

The time change of the differential pressure (P−P₀) in the pipe can beobtained by figuring out the state equation of the gas and it isdetermined depending on a pump characteristic, a leakage characteristic,and a temperature characteristic in pressurization concerning thedifferential pressure (P−Po).

The time change curve of the differential pressure (P−P₀) in the pipe isexpressed with the following fundamental equation.(P−P ₀)=(1/D) (Bq _(0inp)±ρ_(ini) RE)(1−e ^(−Dt))+(P _(ini) P ₀)e^(−Dt)  (1)

Hereinabove, (P_(ini)−P₀) is B=(ρRT₀/V), the initial differentialpressure in the pipe, ρshows a vapor density (ρ_(ini) shows the vapordensity of an initial state), R shows a gas constant, T₀ shows theenvironmental temperature (the gas temperature in the pipe) of aninspection area, and V shows the pipe volume.

In addition, it is D=B(C₊+C⁻), which is a parameter relevant topressurization with a pump, and depressurization by leakage. Thepressurizing rate q_(inp) of the pump relevant to a pressurization termcan be expressed by deducting the effect term C₊(P−P₀) of thepressurizing-side pressure P from fixed pressurizing rate q_(0inp) ofthe pump, and it becomes q_(inp)=q_(0inp)−C₊(P−P₀). Also, since theleakage flow rate q_(out) relevant to the term of leakage becomes thevalue C⁻(P−P₀) proportional to the differential pressure, it becomesq_(out)=C⁻(P−P₀).

Moreover, as a term relevant to a temperature change, the temperaturechange is assumed approximately to be linear in the inspection time andis expressed as temperature change inclination E=|(ΔT(t)/Δt)|.

The pipe volume can be obtained on the basis of the equation (1).Although an exponential function is obtained as solution here, itapproximates the pipe volume up to the secondary term, and thetemperature change in pressurization with pump is ignored since the timeof pressurization with pump is short. Further, the equation (1) can betransformed to the next equation by applying that the initialdifferential pressure (P_(ini)−P₀) in a pipe becomes 0 in pressurizingthe inside of the pipe from the atmospheric pressure.(P−P ₀)=q _(0inp) Bt−(½) q _(0inp) C ₊ B ² t ²  (2)

Here, the solution of the equation (2) is calculated as to the pipevolume V by setting (P−P₀) to P_(d), and substituting B=(ρRT₀/V).$\begin{matrix}{V = {{\left\{ {{\left( q_{0{inp}} \right)\left( {\_ RT}_{0} \right)t} + {\sqrt{\quad}\left( {\left( {\left( q_{0{inp}} \right)\left( {\rho\quad{RT}_{0}} \right)t} \right)^{2} - {4 \times P_{d} \times \left( {1/2} \right)\left( {q_{0{inp}}C_{+}} \right)\left( {\rho\quad{RT}_{0}} \right)^{2}t^{2}}} \right)}} \right\}/2} \times P_{d}}} & (3)\end{matrix}$

It is made possible to calculate the pipe volume from the equation (3),by specifying beforehand the pressurization characteristic (q_(0inp,)C₊) of a pump using the inspection object that comprises the known pipevolume, and then, measuring pressure differential P_(d) inpressurization and the pressurization time t in the actual inspection,and incorporating the measurement value. In addition, as to (ρRT₀),although it is preferable to detect the environmental temperature T₀separately in measuring and to substitute it, it is also possible, incase of simplifying the structure of the device further, to assume(ρRT₀) to be fixed value and to input it to the pressure measuringdevice beforehand.

In setting the environmental temperature T₀, the actually-measuredtemperature of the gas fed into a pipe, the actually-measuredtemperature of the gas discharged from the pipe, or the mean value ofabove-described two values can be used.

Next, the method for calculating the influences of a temperature changewill be explained.

When the pressure in a pipe is equalized to the atmospheric pressurearound the pipe and the pipe is held in the closed state, the equation(1) is expressed as follows.(P−P ₀)=(1/D)(±ρ_(ini) RE)(1−e ^(−Dt))  (4)

It is D=B(C⁻).

Here, by disregarding the term of leakage, expanding equation (4), whichreduces the limit value of D close to zero, into power series of Dt, andputting 0 to D, the next equation will be obtained.(P−P ₀)=(±ρ_(ini) RE)t  (5)

In measurement, the inside of a pipe is adjusted to the atmosphericpressure condition, the pipe is closed, and the pressure change in thepipe within fixed time (for example, about 1 minute) is measured. Thetemperature change in the pipe depends on climate condition, however,since it can be assumed to fluctuate with the same period as thetemperature fluctuations in a day, it is possible to assume thetemperature change in the pipe in a short time to be in a linear state.In addition, on the ground that there is no pressure differentialbetween the inside and the outside of the pipe, it is considered to bein the condition that the influences of leakage can be disregarded, andtherefore, the measurement result is that the time change of the in-pipepressure shows a graph with a certain slope under the influences of thetemperature change as in the equation (5).

Since there sometimes occurs, in practice, a rapid temperature changeeven in the inspection time, it is preferable to measure the pressurechange inside a pipe due to a temperature change before and after, orduring the leakage inspection of a pipe, and to evaluate the influencesof the temperature change frequently. Optimally the influences of thetemperature change (the slope of the time change of the in-pipepressure) measured before and after the leakage inspection correspond toeach other, however, even in case they do not correspond, it is possibleto evaluate the influences of the temperature change in the leakageinspection by calculating the mean value of the said before and aftermeasurement results (the slope of the time change of the in-pipepressure), for the purpose of estimating the influences of thetemperature change in the leakage inspection.

Next, the method for measuring the amount of leakage will be explained.

The pressure change when pressurizing a pipe to pressure P_(ini) andclosing it is expressed by using the equation (1) as follows.(P−P ₀)=(1/D)(±ρ_(ini) RE)(1−e ^(−Dt))+(P _(ini) −P ₀)e ^(−Dt)  (6)

It is D=B(C⁻).

The first term of the right-hand side of the equation (6) is the sameterm as the equation (4), and since the equation (4) can be expressedapproximately as the equation (5), the influences of a temperaturechange is measured separately as described above, the slope (±ρ_(ini)RE)expressed in the equation (5) is calculated, and the influences of thetemperature change is removed from the above-mentioned equation (6). Inparticular, if the leakage inspection differential pressure of removingthe influences of the temperature change is set as (P−P₀)^(*),(P−P₀)^(*)=(P−P₀)−(±ρ_(ini)RE)t is calculated. In addition, ± isselected to be + when the temperature change rises and − when thetemperature change declines respectively.

Thereby, the equation (6) becomes (P−P₀)^(*)=(P_(ini)−P₀)e^(−Dt), andtherefore, the coefficient C, (leakage inclination per differentialpressure, unit [m³/Pa·s]) of the leakage flow rate q_(out) whichdetermines a leakage amount, can be obtained from the next equation.In((P−P ₀)^(*)/(P _(ini) −P ₀))=−Dt=−(ρRT ₀ /V)(C ⁻)t  (7)

Since the pipe volume V is already calculated, the leakage inclination Ccan be determined by the equation (7). Also, as this leakage inclinationC per differential pressure is the value at the same time that indicatesthe amount of leakage, it can also be used as criteria of leakage, andin case the leakage inclination measured has a numeric value above acertain level, it is possible to judge that there occurs leakage.

In addition, if the leakage inclination C⁻ shows the pressuredifferential (P−P₀) between the in-pipe pressure P and the atmosphericpressure P₀, the leakage flow rate at that time can be determined, andthe amount of leakage can be calculated by means of time quadrature ofthe leakage flow rate. Also, when a gas piping receives the usualadjustment pressure P_(gas), the leakage flow rate is calculated byC⁻(P_(gas)−P₀). Accordingly, “the amount of leakage” described in claimshas a comprehensive meaning including not only the above-mentionedamount of leakage itself, but also the leakage flow rate, leakageinclination, and the pressure change value due to leakage.

In the leakage inspection of gas piping, the judgment is performedwhether leakage has occurred from a pipe, besides the method measuringthe amount of leakage, by pressurizing the pipe until fixed pressure,holding it in the closed state, and then, observing the pressure changewithin the fixed time.

Even in this case, since the pressure in the pipe fluctuates widely dueto the influences of a temperature change, an accurate leakageinspection can be realized by evaluating the pressure change by usingthe above-mentioned leakage inspection differential pressure (P−P₀)^(*)of removing the influences of the temperature change.

I.e. by measuring how the leakage inspection differential pressure(P−P₀)^(*) of removing the influences of the temperature changefluctuates after the fixed time on the basis of the differentialpressure (P_(ini)−P₀) in initial pressurization, it can be judged thatthere is leakage if it fluctuates more than the fixed value.

Since the pressure in a pipe is adjusted to be in the atmosphericpressure condition when evaluating the influences of a temperaturechange as described above, it presents the possibility of amending theatmospheric pressure change, which is the factor affecting themeasurement result together with a temperature change in leakageinspection. In other words, since the amount of amendment (correctionvalue under the influences of a temperature change) is measured on thebasis of the current atmospheric pressure, and the value itself thatchanges in accordance with the change of the atmospheric pressureconstantly becomes the standard value, the measurement result hardlyreceives the influences of atmospheric pressure change.

Since the bigger the pipe volume is, the more slowly the pressurechanges although it depends on the amount of leakage, it is necessary toimplement long-time leakage inspection. In legal items of inspection ofLP gas, it is required to take 5 minutes for the measurement in case thepipe volume is below 2.51 (unit 1: liter) and over 10 minutes in case itexceeds 2.51.

Therefore, as it is possible to calculate the pipe volume as mentionedabove in the pressure measuring method of the present invention, itpresents the possibility of setting up the measurement time amountautomatically or displaying or instructing the necessary measurementtime amount for inspection providers on the basis of this calculationresult, and accordingly, the excessive and useless measurements areeliminated, and an efficient inspection is realized.

As the method for eliminating the influences of a temperature change, itis also possible to measure the temperature of the gas in a pipedirectly and to calculate temperature change inclination E in additionto the above-mentioned method.

Also, when measuring the above-described various differential pressuresor temperature change inclination, etc., besides the measurement withtwo points, initial point and terminal point, it is possible to detectthe measurement values of more than three points and calculate them bystraight-line approximation of a least square, a regression line, etc.

Next, one example of the pressure measuring method of the presentinvention will be explained on the basis of the flow chart of FIG. 4. Ineach step of the flow chart, the operating instructions, whichinspection providers should follow, are arranged to be displayedsequentially in the liquid crystal display part. The pressure measuringdevice of the present invention is designed so that even someoneinexperienced in it can easily handle it.

Firstly, the switch of the power source key of the pressure measuringdevice is turned on. Although not shown in FIG. 4, the initial settingor selection of various measurement modes, etc. of the pressuremeasuring device, are already made possible at this moment. Generalmeasurement mode is explained in FIG. 4.

Input will be completed, by inputting a customer name or a code andpressing SET key in accordance with the instructions of the liquidcrystal display part.

Next, in order to reduce the pressure signal level, that the pressuresensor 4 indicates under the present atmospheric pressure, to zerovalue, the offset adjustment of the pressure sensor 4 is conducted (forexample, a duration is set to about 5 seconds).

Then, instructions of closing meter cock, or of connecting theconnecting portion 1 of the measuring device to the pipe that is anobject of inspection, etc. are issued on the display part.

Then, the valve 7 is opened and the pressure in a pipe is equalized tothe atmospheric pressure outside the pipe. Instead of this valve 7, byinstalling a T-shape pipe which is set in a part of the detection hose 2and the connecting portion 1 and is communicated with outside, equippingthe part of the said T-shape pipe with a manual valve that controls thecommunication condition with the outside, and then, opening this manualvalve, the in-pipe pressure of the pipe that is an object of inspectioncan be also equalized to the atmospheric pressure.

Then, the valve 7 is closed and the inside of the pipe is held in theclosed state. The pressure change in the pipe is measured for about 60seconds. In the measurement time, an operating condition, such as“measuring a temperature change”, a numeric value or a graph of pressurechange are displayed on a display part.

After the measurement time, the amount of pressure change is calculatedper unit time from the measurement value of the pressure change.

When the said amount of pressure change is within the given value, it isjudged that there are no influences of a temperature change (thepressure change in a pipe due to the temperature change in themeasurement), and the next step of inspection will be implemented.

When the absolute value of the said amount of pressure change hasfluctuated beyond the given value, it is judged that there areinfluences of a temperature change, and at the same time, it ismemorized whether a pressure is on the rise or on the decline. Then, thefollowing step of inspection will be implemented.

With the electric pump 5 driving, and the gating of the valve 3 beingcontrolled, the inside of a pipe is pressurized to the given pressure(usually 5.4 kPa, or it is preferable to add the given pressure toatmospheric pressure in order to eliminate the influences of atmosphericpressure change) by injecting air into the pipe. After completion of thepressurization, the electric pump 5 is promptly stopped and the valve 3is closed.

And then, by measuring the pressure differential P_(d) by pressurizationand the pressurization time t, and substituting them into theabove-mentioned equation (3), the pipe volume V is calculated.

As to the calculation results, the pressure inside a pipe aftercompletion of the pressurization (for example, 5.4 kPa), the pipe volumeV, and the measurement time necessary for a leakage inspection (over 5minutes or over 10 minutes, or the time amount in proportion to a pipevolume) are displayed, and the inspection is initiated. In addition, itis also possible to display numerical values in the measurement, orcontents of a measurement being preformed, on the display part.

After completion of the measurement, the amount of pressure change (theamount of pressurization change) per unit time after pressurization iscalculated from the measurement value of the pressure change.

Then, in case there are no influences in the judgment of influences oftemperature change which was obtained in the above, and also, the amountof pressurization change is within the predetermined amount, (in casethere is no pressure change), it is judged that nothing is peculiar (noleakage).

Also, although not shown in the figures, even in case there areinfluences of temperature change, by subtracting the amount of pressurechange due to the influences of temperature change from theabove-mentioned amount of pressurization change, it can be judged thatnothing is peculiar if the numerical value of the pressure change amountof removing the influences of temperature change, is within thepredetermined value.

Also, by calculating the above-mentioned leakage inclination C⁻, not theamount of pressure change itself, it can be judged whether there isleakage or not in accordance with the said leakage inclination value.

In addition, when the measurement time is terminated, the completion ofthe measurement can be made known by ringing the electronic sound of thespeaker that is not shown in the figures. It is also possible that inoperating KEY board, in the steps of inputting various data, or at thestart and the end of various inspection steps, the electronic soundsring with the rhythm and pitch of the sound changing if required.

Next, in order to re-inspect the influences of temperature change, onceagain by opening the valve 7, adjusting the in-pipe pressure to be inthe atmospheric pressure condition, and then, holding the pipe in theclosed state, the amount of pressure change in the pipe is measured over60 seconds as the former measurement of the influences of temperaturechange.

At this point, if both the amount of pressure change at the first timeand the second time rise, it is judged whether there is leakage or notin accordance with the numeric value of the amount of pressure changewherein the influences of temperature change is eliminated bycalculating the mean value of both the amounts of pressure change andsubtracting the said mean value from the amount of pressure change inthe leakage inspection. In addition, in case that both the amount ofpressure change at the first time and the second time decline, it isprocessed and judged likewise.

However, if the first time and the second time show different changes(for example, the one shows a rise and the other shows a decline), it isconsidered to be an invalid inspection and the re-inspection will beimplemented from the first measurement of the influences of temperaturechange.

Next, legal items of inspection will be inspected.

Firstly, it is directed on an display part that the connecting portion 1of the pressure measuring device should be connected to the pipe (oneend of a purpose-built T-shape coupling pipe, or one of the pipes withtwo gas cocks) which diverges from a part of the pipe connecting theregulator to be inspected and a burning appliance, such as stove burner.Then, the opening of the valve of meter cock and LP gas vessel isinstructed. With the condition that gas is fed into the burningappliances being retained, the pressure is measured by means of thepressure sensor 4.

The gas pressure at this point is registered as “adjustment pressure”.

Then, it is directed to ignite the burning appliance, and “combustionpressure” that is a gas pressure in combustion is measured.

Finally, “blockade pressure” that is a gas pressure in extinguishing theburning appliance is measured and registered.

It is set out that each pressure measurement time amount takes at leastsixty seconds respectively.

It is judged to be normal, in judging conditions of various pressures,when “adjustment pressure” is within 2.3˜3.3 kPa, “combustion pressure”is below the adjustment pressure and within 2.0˜3.3 kPa, and “blockadepressure” is above the combustion pressure and below 3.5 kPa. Themeasurement values or the judgment results are displayed on a displaypart.

When all the inspection items have been completed, it is possible tore-display the results of each leakage inspection and check the contentsby pushing the navigation key of KEY board as appropriate.

In addition, in measuring a pipe volume and the legal items ofinspection, the past measurement data of the same client can bearranged, by calling it up from the memorizing means 10, to be displayedas reference information and to be contrasted with the presentmeasurement value on display. Accordingly, it can be used as referenceof relative judgment whether the present measurement result is withinthe range of normality or not.

It is possible to check the inspection result, to register it in thememorizing means 11 if required, and also, to call up and display theregistered contents again, and check it.

When all the inspections have been finished, it is directed to close thegas cock, to remove the connecting portion 1 from a pipe, etc. and then,to switch off the pressure measuring device. As to switching off thedevice, it can be arranged to be switched off automatically in casethere has been no operation of KEY board, etc. for certain amounts oftime.

Besides the above-mentioned pressure measuring method, in order toevaluate the influences of temperature change, the influences oftemperature change can be eliminated more accurately by repeating themeasurement of the amount of pressure change due to a temperature changefor one minute, and the measurement of the amount of pressure change forone minute after pressurization, alternately, and measuring thetemperature change within the inspection time amount frequently.

At this point, it is possible to change the repeating frequency inaccordance with the pipe volume that is an object of inspection, and tocontinue until the accumulated amount of the measurement time of thepressure change amount after pressurization becomes the given value (forexample, more that five minutes).

Also, the elimination of the influences of temperature change can beapplied to various cases, such as the method of subtracting the meanvalue of the amounts of pressure change due to the influences of thetemperature change before and after measuring amount of pressure changeafter pressurization, from the measured amount of pressure change afterpressurization, or the method of subtracting the mean value of all theamounts of pressure change due to the influences of temperature change,from the mean value of all the measured amounts of pressure change afterpressurization.

In the above-mentioned pressure measuring method, the pressurizing stepfor measuring the volume of a pipe is used at the same time as thepressurizing step for a leakage inspection; however, a pressurizing stepcan be installed separately for measuring the volume of a pipe.

Moreover, in case of measuring the volume of a pipe, it is also possibleto measure the temperature of the gas fed into a pipe, or dischargedfrom the pipe, directly by means of a temperature sensor, and to use itas the environmental temperature T₀.

In addition, if the pipe volume is known beforehand, the numeric valueof the said pipe volume can be inputted from KEY board without measuringit, and used for a leakage inspection etc.

Although the case of pressurizing the inside of a pipe was exemplifiedin the above-mentioned pressure measuring method, it is also possible tomeasure the pipe volume or the leakage amount likewise by depressurizingthe inside of the pipe (putting the inside of the pipe into a negativepressure condition).

Also, by combining the measurements in pressurization anddepressurization, for example, after it is judged that there is aleakage by means of the pressurization measurement, it is possible tore-judge it by implementing the depressurization measurement.

In addition, “a pressurizing and depressurizing step” as in claims means“a step for pressurizing or a step for depressurizing”.

In the above-mentioned pressure measuring method, leakage can be judgedonly after the completion of the measurement of the pressure changeamount in a leakage inspection. Therefore, by using the value of thepressure change amount that measured the influences of the temperaturechange before the leakage inspection, predicting the pressure changeamount in the leakage inspection after pressurization (calculate thechange amount in case there is no leakage, and the change amount withinthe limits of what is allowed as a measurement deviation against thesaid change amount), and comparing the said predicted value with theactually-measured pressure change amount after pressurization, thejudgment of leakage is possible at any time in the leakage inspection.

Furthermore, in the above-mentioned pressure measuring method; theamount of pressure change due to the influences of a temperature changeis measured before and after the leakage inspection in order to removethe influences of a temperature change. However, as there occurs atemperature change even in the leakage inspection (not only in theleakage inspection but also in the inspections of adjustment pressure,combustion pressure, blockade pressure, etc.), in order to ensure moreaccurate inspection, it is also possible to measure the gas temperatureinside a pipe, or the temperature of the pipe, in the leakage inspectiondirectly by means of a temperature sensor, and to calculate temperaturechange inclination E.

Also, by using the measurement of the pressure change amount due to theinfluences of a temperature change and the measurement by means of atemperature sensor together, it presents the possibilities, such as toamend the value of the pressure change amount due to the temperaturechange by using the value measured by the temperature sensor, or, evenin case the above-mentioned predicted value differs significantly fromthe actually-measured pressure change amount after pressurization, tojudge accurately by using the measured value of said temperature sensorwhether the difference between the predicted value in the temperaturechange and actually-measured value is due to a temperature change or aleakage.

The example of the measurement result by the pressure measuring deviceof the present invention is shown in FIG. 5.

The pipe to be inspected was measured with the settings that a hole forleakage was made in a part of the pipe, which was heated gradually forabout 180 seconds from the beginning, and after the fixed temperaturewas maintained until around 360 seconds, the temperature was lowered.

The horizontal axis of the graph in FIG. 5 represents time, and thevertical axis represents the amount of differential pressure change(P−P_(ini)) between the differential pressure of the pressure P inside apipe and the atmospheric pressure P₀, and the differential pressure ofthe initial pressure P_(ini) and the atmospheric pressure P₀.

Accordingly, when measuring the influences of a temperature change, itis P_(ini)=P₀. For example, in the leakage inspection afterpressurization, it is P_(ini)=5.4 kPa.

As in the graph of FIG. 5, the amount of pressurization change in theleakage inspection differs in accordance with the temperature change,and it is apparent that it enables the measurement to follow thetemperature change. With the existing pressure measuring devices, whichdoes not take a temperature change into consideration, the leakageinspection of a pipe like this was entirely difficult.

Not being limited to the pressure measuring method and device explainedhereinabove, the present invention enables to display graphically on thedisplay part and select numeric value display or graphic display, and toselect the digit number of displayed value, for example, in 0.02 kPaunit that is designated by law, bigger or smaller unit than it. Also, itenables the input of an operating schedule or the register of aninspecting date and hour by adding a displaying function of calendar andclock.

Thus, it goes without saying that various functions utilized in theexisting electronics devices can be added to the present invention ifrequired.

In addition, in the embodiments of the present invention, a gas pipingwas centrally explained, however, it is possible to apply pipes feedingother gases or liquids. Moreover, although it was exemplified that gaswas injected to a pipe for pressurizing the inside of the pipe, liquidcan be also injected. In this case, of course each measurement isimplemented by taking into consideration the difference of the conditionand the characteristics of gas and liquid.

INDUSTRIAL APPLICABILITY

The present invention enables not only the appropriateness of inspectiontime, but also the accurate calculation of leakage amount as it canmeasure the volume of a pipe easily.

In addition, since the elimination of the influences of a temperaturechange is made possible, it enables an accurate leakage inspection evenwhen and where a rapid environmental change occurs.

Moreover, by incorporating an electric pump, as a pressurizing means,into the pressure measuring device, portability and operationality areimproved, and by displaying not only the numerical value measured orcalculated, but also operation instructing information or operatingcondition, it presents the possibility for even inexperienced inspectionproviders to handle it easily.

Further, as it has functions, such as calling up the past measurementresults and accumulating the necessary measurement results, a variety offorms of utilization concerning the pressure measuring device arepossible.

1. (Cancelled).
 2. A pressure measuring method which, by the connectionto a pipe for feeding a gas or a liquid, measures the pressure in thesaid pipe, comprising a pressurizing and depressurizing step forpressurizing or depressurizing the inside of the pipe held in the closedstate, and a step for measuring an amount of pressure change of the pipein the standing state after completion of the said pressurizing anddepressurizing step, wherein; before the said pressurizing anddepressurizing step or after completion of the measurement of the amountof pressure change in the standing state, the said pipe is closed afteradjusting the in-pipe pressure to the pressure outside the pipe, and theamount of pressure change in the pipe due to a temperature change ismeasured, and the value of the said amount of pressure change in thestanding state is amended in accordance with the said amount of pressurechange due to the temperature change, and the influences of thetemperature change on the pressure change in the standing state areeliminated.
 3. A pressure measuring method which, by the connection to apipe for feeding a gas or a liquid, measures the pressure in the saidpipe, comprising a pressurizing and depressurizing step for pressurizingor depressurizing the inside of the pipe held in the closed state, and astep for measuring an amount of pressure change of the pipe in thestanding state after completion of the said pressurizing anddepressurizing step, wherein; before the said pressurizing anddepressurizing step or after completion of the measurement of the amountof pressure change in the standing state, the said pipe is closed afteradjusting the in-pipe pressure to the pressure outside the pipe, and theamount of pressure change in the pipe due to a temperature change ismeasured, an amount of pressurization and depressurization change of thein-pipe pressure by the said pressurizing and depressurizing step or anadditional pressurizing and depressurizing step, and the flow rate ofthe gas or the liquid which is fed into, or discharged from the pipeduring the pressurization or the depressurization, are measured, thevolume of the pipe in the closed state is calculated on the basis of thesaid amount of pressurization and depressurization change, and the saidflow rate of the gas or the liquid, the value of the said amount ofpressure change in the standing state is amended in accordance with thesaid amount of pressure change due to the temperature change, and theamount of leakage of the gas or the liquid from the pipe is calculatedon the basis of the said amended amount of the pressure change in thestanding state and the said volume of the pipe.
 4. A pressure measuringmethod which, by the connection to a pipe for feeding a gas or a liquid,measures the pressure in the said pipe, comprising a pressurizing anddepressurizing step for pressurizing or depressurizing the inside of thepipe held in the closed state, and a step for measuring an amount ofpressure change of the pipe in the standing state after completion ofthe said pressurizing and depressurizing step, wherein; before the saidpressurizing and depressurizing step, the said pipe is closed afteradjusting the in-pipe pressure to the pressure outside the pipe, and theamount of pressure change in the pipe due to a temperature change ismeasured, the predicted value of the said amount of pressure change inthe standing state is calculated in accordance with the said amount ofpressure change due to the temperature change, and leakage condition ofthe said pipe is judged by comparing the said predicted value with theactually-measured amount of pressure change in the standing state. 5.(Cancelled)
 6. (Cancelled)
 7. The pressure measuring method as claimedin claim 3, wherein; at least one of the actually-measured temperatureof the gas or the liquid that is fed into a pipe, and theactually-measured temperature of the gas or the liquid that isdischarged from the said pipe, is used in calculating the said volume ofthe pipe.
 8. The pressure measuring method as claimed in claim 2,wherein; in measuring the said amount of pressure change in the standingstate, the said amount of pressure change is re-amended on the basis ofthe amount of change of the actually-measured temperature of the gas orthe liquid in the pipe, or the actually-measured temperature of thepipe.
 9. The pressure measuring method as claimed in claim 2, wherein;when measuring the pressure several times, the said pressurizing anddepressurizing step is conducted by doing the pressure measurement inpressurization condition and the pressure measurement indepressurization condition in combination.
 10. The pressure measuringmethod as claimed in claim 3, wherein; the amount of time for measuringthe said amount of pressure change of the pipe in the standing state isdecided in accordance with the value of the said volume of the(Amendment of claims) pipe.
 11. The pressure measuring method as claimedin claim 2, wherein; the said amount of pressure change is calculated byapproximating several measurement values by straight line.
 12. Thepressure measuring device which uses the pressure measuring method asclaimed in claim
 2. 13. The pressure measuring device as claimed inclaim 12, including; a pressurizing means for pressurizing the inside ofthe pipe in the inside of said pressure measuring device.
 14. Thepressure measuring device as claimed in claim 12, including; a displaypart placed in the said pressure measuring device, which displays atleast one of the numerical values measured or calculated by the saidpressure measuring device, information of operator guidance or operatingcondition of the said pressure measuring device, and the past result ofthe measurement or calculation.
 15. The pressure measuring device asclaimed in claim 12, including; a memorizing means which accumulates thenumerical values measured or calculated.